"It was Red Sonya who had come to his aid, and her onslaught was no less terrible than that of a she-panther. Her strokes followed each other too quickly for the eye to follow; her blade was a blur of white fire, and men went down like ripe grain before the reaper."
If you have not read The Shadow of the Vulture by Robert E. Howard you should give it a try. It is available on Project Gutenberg Australia's site here. This is the story that brought Red Sonja to the world as Sonya of Rogantino. Rather than a fantasy setting, this takes place during the seige of Vienna by the Turks (1529). Despite the realistic setting, Sonya is very much the Sonja we know. I did two reviews, a while back, at Adventures in Nerdliness (part 1, part 2).
"And with a scornful flirt of her wide coattails, she swaggered off down the battlements, giving back promptly and profanely the rude sallies of the soldiers. Gottfried scowled after her, and a Lanzknecht slapped him jovially on the shoulder. 'Eh, she's a devil, that one! She drinks the strongest head under the table and outswears a Spaniard. She's no man's light o' love. Cut—slash—death to you, dog-soul! There's her way.'"